It's difficult to believe that Tony Kushner's uncannily prescient Homebody/Kabul was written before the awful events of 11 September and the subsequent war on Afghanistan. But the play, far from being rendered out-of-date by what the playwright frighteningly anticipates in it, actually becomes a long-winded but nevertheless alert and urgent contribution to trying to grasp how and why it happened.

In the most directly chilling part of the play, a character attributes earlier alleged American military support of the Taliban to the US wanting to use that regime to settle a 20-year-old score with Iran."You love the Taliban so much, bring them to New York! Well, don't worry, they're coming to New York!" she shouts. Wow!

It's a line that resonates with amazing perspicacity, in a play that is always deeply thought intellectually but not always deeply felt emotionally. Too often, Kushner seems to be indulging in the typical Stoppard shortcoming of creating mouthpieces rather than credible characters; and like Stoppard, he can't resist showing off his facility for words either.

He can be forgiven, however, in the case of the Homebody of the first half of the title, a London housewife fascinated by the ancient land of Afghanistan who opens the play with a dazzling monologue made up of her knowingly convoluted verbiage. Here, the showing off comes from the character as much as from the writer; but there's no showing off in Kika Markham's breathtakingly realised performance - a model of precise understatement. The monologue was originally written for her, and performed on its own by her at London's Chelsea Centre in 1999.

Now a mere appetizer before the main course of the play itself, dramatically, it remains more filling than what follows. The Homebody disappears to Afghanistan where her husband and daughter later try to track her, or her dead body, down. As a master chef of playwriting, Kushner is hardly prolific - his last major work was Angels in America, first staged over a decade ago - but he's certainly prodigious in what he does write. The two-part Angels famously ran over seven hours; this is nearly four.

The stew that results from the multiple ingredients Kushner throws into Homebody/Kabul emerges sometimes tasty, sometimes indigestible - but, while unquestionably dense and demanding, it also repays the investment in time and effort. The ideas contained here are so stimulating and provocative that you feel constantly challenged during this evening of profound, weighty and discursive debate which, in Declan Donnellan's stark production on a bare wooden platform, holds your attention throughout.

- Mark Shenton